Process for preparing block copolymer and resulting composition

ABSTRACT

Lithium-terminated polymers of one or more conjugated dienes and of one or more mono alkenyl arenes are coupled by reaction with an alkoxy silane coupling agent having the formula R x —Si—(OR′) y , where x is 0 or 1, x+y=4, R and R′ are the same or different, R is selected from aryl hydrocarbon radicals, linear alkyl hydrocarbon radicals and branched alkyl hydrocarbon radicals, and R′ is selected from linear and branched alkyl hydrocarbon radicals, such that the resulting polymer composition contains less than about ten weight percent of uncoupled polymer diblock. The polymer compositions are subsequently selectively hydrogenated, and are useful in a variety of compounds and end use applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 10/454,237, filed Jun. 4, 2003, entitled Process for Preparing BlockCopolymer and Resulting Composition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the coupling of anionic polymers and to thehydrogenation of such coupled polymers to make a polymer compositioncontaining low levels of uncoupled polymer and a mixture of linear andradial polymers.

2. Background of the Art

The coupling of lithium-terminated polymers is a process known in theart. In accordance with this known process, a lithium-terminated polymeris treated with a compound having two or more functional groupscontaining two or more reactive sites capable of reacting with thecarbon-lithium bonds of the lithium-terminated polymer. In many casesthe multifunctional coupling agent thereby becomes a nucleus for theresulting structure. From this nucleus long chain polymeric branchesradiate and such coupled polymers have specific properties that renderthem useful for particular applications.

Linear polymers are formed by employing coupling agents having tworeactive sites. For example, one coupling agent employed in makinglinear polymers is methyl benzoate as disclosed in U.S. Pat. No.3,766,301. Radial polymers are formed by employing coupling agentshaving more than two reactive sites. Examples of such coupling agentsinclude among others silica compounds, including silicon tetrachlorideand alkoxy silanes—U.S. Pat. Nos. 3,244,664, 3,692,874, 4,076,915,5,075,377, 5,272,214 and 5,681,895; polyepoxides, polyisocyanates,polyimines, polyaldehydes, polyketones, polyanhydrides, polyesters,polyhalides—U.S. Pat. No. 3,281,383; diesters—U.S. Pat. No. 3,594,452;methoxy silanes—U.S. Pat. No. 3,880,954; divinyl benzene—U.S. Pat. No.3,985,830; 1,3,5-benzenetricarboxylic acid trichloride—U.S. Pat. No.4,104,332; glycidoxytrimethoxy silanes—U.S. Pat. No. 4,185,042; andoxydipropylbis(trimethoxy silane)—U.S. Pat. No. 4,379,891.

The production of styrenic block copolymers such as S-E/B-S triblocks bycoupling has a number of process advantages over sequentialpolymerization, such as better control over the styrene block size andlower viscosity during polymerization. However, the inevitable presenceof un-coupled arms can limit product performance. Diblock contaminationcan greatly reduce tensile strength and related properties in a triblockcopolymer or compound thereof. S-E/B-S polymers for use in applicationssuch as highly-oiled compounds cannot afford to sacrifice in this area.It is generally difficult to achieve coupling efficiencies of betterthan 90%. While coupling efficiencies on the order of 90% can beachieved by reaction with m-divinylbenzene, the resulting products arehigh molecular weight “star” polymers. Although the melt viscosity ofsuch a polymer is much lower than a linear product of the same totalmolecular weight, it is much higher than that of the correspondingtriblock that would be prepared by coupling two of the diblock arms.

It would be highly desirable to identify a coupling agent that givesgreater than 90% of a substantially linear product, or, at least, amixture of linear and radial polymers. It would be particularlyadvantageous if coupling efficiencies approaching 95% could be obtainedin systems that result in a butadiene microstructure suitable forhydrogenation to give a saturated rubber block. Such products would beexpected to have properties that are comparable to sequentiallypolymerized S-E/B-S polymers, which are often contaminated with somediblock due to a variety of side reactions. It would also be highlyadvantageous if residual coupling agent or its by-products were found tohave no adverse affect on the activity of the hydrogenation catalyst.

SUMMARY OF THE INVENTION

The present invention broadly encompasses a process for making ahydrogenated block copolymer, comprising the steps of: a. reacting aliving lithium-terminated polymer having the formula P-Li where P is acopolymer chain of one or more conjugated dienes having 4 to 12 carbonatoms and one or more mono alkenyl arenes having 8 to 18 carbon atomswith an alkoxy silane coupling agent having the formulaR_(x)—Si—(OR′)_(y), where x is 0 or 1, x+y=4, R is selected from aryl,linear alkyl and branched alkyl hydrocarbon radicals, and R′ is selectedfrom linear and branched alkyl hydrocarbon radicals, and where the molarratio of Si to Li is between about 0.35 and about 0.7, thereby forming acoupled polymer; b. optionally hydrogenating the coupled polymer underhydrogenation conditions of a catalyst, time, temperature and pressureeffective to substantially saturate at least the olefinically deriveddouble bonds of said coupled polymer without substantial degradation ofthe coupled polymer; and c. recovering the resulting polymer.

The present invention also encompasses the resulting block copolymersmade using the alkoxy silanes of the process. In particular, the presentinvention includes a block copolymer composition comprising: a. atetra-branched block copolymer (IV) having a number average molecularweight of 100,000 to 800,000 represented by the general formula (A-B)₄X;b. a tri-branched block copolymer (III) having a number averagemolecular weight of 75,000 to 600,000 represented by the general formula(A-B)₃X; c. a di-branched block copolymer (II) having a number averagemolecular weight of 50,000 to 400,000 represented by the general formula(A-B)₂X; and d. a linear diblock copolymer (I) having a number averagemolecular weight of 25,000 to 200,000 represented by the general formulaA-B; where: i) A represents a polymer block of a mono alkenyl arene; ii)B represents a polymer block of a conjugated diene; iii) X representsthe residue of an alkoxy silane coupling agent; and iv) the relativeamounts of copolymers I, II, III and IV are 0 to 5 weight percent IV, 0to 60 weight percent III, 40 to 95 weight percent II and 2 to 10 weightpercent I, where the total of I, II, III and IV equals 100 weightpercent. The alkoxy silane coupling agent has the formulaR_(x)—Si—(OR′)_(y), where x is 0 or 1, x+y=4, and R and R′ are the sameor different, R is selected from aryl hydrocarbon radicals, linear alkylhydrocarbon radicals and branched alkyl hydrocarbon radicals, and R′ isselected from linear or branched alkyl hydrocarbon radicals having 1 to12 carbon atoms.

Also contemplated by the present invention is a block copolymercomposition comprising: a. a tetra-branched block copolymer (IV) havinga number average molecular weight of 100,000 to 800,000 represented bythe general formula (C-D-E)₄X; b. a tri-branched block copolymer (III)having a number average molecular weight of 75,000 to 600,000represented by the general formula (C-D-E)₃X; c. a di-branched blockcopolymer (II) having a number average molecular weight of 50,000 to400,000 represented by the general formula (C-D-E)₂X; and d. a lineartriblock copolymer (I) having a number average molecular weight of25,000 to 200,000 represented by the general formula C-D-E; where: i) Drepresents a polymer block of a mono alkenyl arene; ii) E and Crepresent polymer blocks of a conjugated diene; iii) X represents theresidue of an alkoxy silane coupling agent; iv) the weight ratio ofpolymer block D to polymer block E is from 10:90 to 90:10; and v) therelative amounts of copolymers I, II, III and IV are 0 to 5 weightpercent IV, 0 to 60 weight percent III, 40 to 95 weight percent II and 2to 10 weight percent I, where the total of I, II, III and IV equals 100weight percent. Still further, rather than a structure (C-D-E)X for thearm, the polymer arm may be (F-G-H)X where F represents a polymer blockof a mono alkenyl arene, G represents a polymer block of a conjugateddiene, and H represents a polymer block of a different conjugated diene.

The present invention affords a robust process for making highlycoupled, saturated (hydrogenated) anionic block copolymers. Excellentcoupling efficiencies have been realized over a broad range of couplingagent to living chain end molar ratios. For many coupling agents,careful control of the coupling agent to chain end ratio is required toachieve even minimal levels of coupling. The process of the presentinvention is remarkably forgiving in this regard.

Coupling efficiency is of critical importance in the synthesis of blockcopolymers, which copolymers are prepared by a linking technology. In atypical anionic polymer synthesis, prior to the coupling reaction, theunlinked arm has only one hard segment (typically polystyrene). Two hardsegments are required in the block copolymer if it is to contribute tothe strength mechanism of the material. Uncoupled arms dilute thestrength forming network of a block copolymer that weakens the material.The very high coupling efficiency realized in the present invention iskey to making high strength, coupled, block copolymers.

The melt viscosity of a polymer increases with increasing molecularweight. Low melt viscosity is preferred for ease of melt processing in apolymeric material. The present invention allows an efficientpreparation of highly coupled polymer for good strength withoutexcessive formation of highly branched products, which products wouldcontribute to unacceptably high melt viscosities. The present inventionaffords predominantly two arm and three arm coupled products with smallamounts of the strength diluting uncoupled arms and four arm coupledproduct that contributes to excessive melt viscosity. The use ofdivinylbenzene, DVB, as a coupling agent for anionic polymers forexample cannot be controlled in this way. When DVB is used in a way thatgives high levels of coupling, it is common to get 6 to 20 or more armslinked together in a single molecule. The affect of these high molecularweight polymers on melt viscosity is known. The present couplingtechnology allows the preparation of high strength block copolymers withgood melt processing characteristics.

It is desirable to hydrogenate butadiene and isoprene containingpolymers to enhance their thermal and oxidative stability. The C═Cunsaturation in diene polymers is prone to degradation at hightemperatures and in the presence of oxygen.

The hydrogenation of silicon coupled anionic polymers has found to beproblematic. A variety of silicon agents outside the scope of thepresent invention were used to make coupled anionic diene polymers;these polymers were hydrogenated using a number of different standarddiene polymer hydrogenation techniques. Degradation of the coupledpolymers during hydrogenation was observed. From gel permeationchromatography (GPC) analyses of the degraded products, it appeared asthough the coupled polymers were decoupling under the hydrogenationconditions.

With the silicon coupled anionic polymers, the decoupling reactionproceeds to form unlinked arms that erode the strength forming networkof the hydrogenated block copolymer. In some examples, most of theproduct was degraded before the hydrogenation reaction was completed. Inthe present invention, we have discovered a means for overcoming thisproblem—it has been found desirable to add an alcohol (such as methanolor 2-ethyl hexanol) after polymerization and prior to hydrogenation. Forexample, when the simplest member of the family of tetraalkoxy silanes,tetramethoxysilane, has been used as the coupling agent to link dienecontaining block copolymer arms, the product polymer should be treatedwith an equivalent of an alcohol (alcohol/P-Li=1 (mol/mol)), such asmethanol, for every equivalent of living anionic polymer arm that was inthe cement prior to the addition of the coupling agent. The alcoholshould be added after coupling and before contacting the coupled polymercement with the hydrogenation catalyst.

Hydrogenation using a standard Ni/Al, Co/Al or Ti technique under theseconditions allowed the formation of a fully saturated polymer withsubstantially no degradation. The present invention is a process formaking hydrogenated, silicon coupled, anionic, diene block copolymerswithout severe degradation. Alternatively, it has been discovered thathigher molecular weight homologues of the tetraalkoxysilane family canbe used to prepare highly coupled, anionic diene copolymers that may behydrogenated with Ni/Al, Co/Al or Ti techniques without seriousdegradation using far less alcohol than was required for thetetramethoxysilane coupled polymers. The use of coupling agents liketetraethoxysilane and tetrabutoxysilane afforded highly coupled polymersthat were not degraded during hydrogenation. These polymers were strong,were readily melt processed, and had excellent thermal and oxidativestability. Likewise, when using trialkoxy silanes such as methyltrimethoxy silane it was found useful to add an alcohol (e.g. 2-ethylhexanol) after coupling and before contacting with a hydrogenationcatalyst in order to avoid any degradation during hydrogenation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the coupling efficiency after hydrogenation of polymersmade with tetramethoxy silane and with tetraethoxy silane as a functionof methanol addition prior to hydrogenation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one embodiment, the present invention is a process which includes astep of reacting a living lithium-terminated polymer having the formulaP-Li where P is a copolymer chain of one or more conjugated dieneshaving 4 to 12 carbon atoms and one or more mono alkenyl arenes having 8to 18 carbon atoms with the alkoxy silane coupling agent. The preferredacyclic conjugated dienes that can be polymerized into the polymer chainP of the present invention are those containing 4 to 8 carbon atoms.Examples for such conjugated dienes are 1,3-butadiene (termed“butadiene” in the claims and elsewhere in the specification),2,3-dimethyl-1,3butadiene, piperylene, 3-butyl-1,3octadiene, isoprene,2-phenyl-1,3-butadiene.

Mono alkenyl arenes that can be polymerized together with the dienes toform the polymer chain P are preferably those selected from the group ofstyrene, the methylstyrenes, particularly 3-methylstyrene, thepropylstyrenes, particularly 4-propylstyrene, the butyl styrenes,particularly p-t-butylstyrene, vinylnapthalene, particularly1-vinylnapthalene, cyclohexylstyrenes, particularly 4-cyclohexylstyrene,p-tolylstyrene, and 1-vinyl-5-hexylnaphthalene.

The polymer chains P can be homopolymers of the conjugated dienemonomers defined or can be copolymers of diene monomers and monoalkenyl-substituted aromatic monomers. The copolymers, in turn, can berandom or tapered copolymers, as well as block copolymers of thesevarious monomers. The presently preferred monomers are isoprene,1,3-butadiene and styrene. The presently preferred polymer chains P arethose where the conjugated dienes are present in a major amount and themono vinyl-substituted arenes are present in a minor amount. It ispreferred that the mono alkenyl arene content be from about 5 to about50 weight percent of the total block copolymer, more preferably fromabout 10 to about 35 weight percent.

The preferred polymer of the present invention is one that is obtainedby coupling a living lithium-terminated polymer selected from the groupconsisting of homopolymers of conjugated dienes having from 4 to 12carbon atoms and copolymers of at least one diene of from 4 to 12 carbonatoms.

Those polymers in which the polymer chain P has a structure A-B- orC-D-E- or F-G-H- so that B or E or H is attached to the coupling agent,and in which A, D and F represents a block of mono alkenyl arenes,preferably a polystyrene block, and B, C, E, G and H represents a blockthat confers rubbery properties to the polymer chain, such as a polyconjugated diene block, a copolymer block of a conjugated diene and amono alkenyl-substituted arene, or a combination of such blocksconstitutes a presently preferred polymer. Such a polymer exhibitsproperties both of an elastomer and of a thermoplastic polymer.Therefore, such polymers can be formed into articles by standardprocedures known for producing articles from thermoplastic polymerswhile the finished article exhibits elastomeric properties.

Furthermore, specific polymers constituting preferred embodiments ofthis invention are those obtained by reactions and procedures disclosedin detail in the following description of a process to make thesepolymers.

In accordance with another embodiment of this invention, there isprovided a process for making the polymers defined above which comprisesa coupling reaction between a living polymer having the formula P-Li anda coupling agent as defined above, wherein Li is lithium and P is asdescribed above.

The quantity of coupling agent employed with respect to the quantity ofliving polymers P-Li present depends largely upon the degree of couplingand the properties of the coupled polymers desired. Preferably thecoupling agent defined above will be employed in a range of from about0.35 to about 0.7 moles of coupling agent per mole of lithium, P-Li,more preferably from about 0.4 to about 0.55 moles of coupling agentbased upon the moles of lithium present in the polymer, P-Li, mostpreferably about 0.45 moles of coupling agent per mole of lithium, P-Li.At lower silicon coupling agent to lithium chain end molar ratios Si/Li(mol/mol), there is not enough coupling agent present to allow highlevels of coupling; the coupling efficiency will start to decline iflower Si/Li molar ratios are employed. Lower levels of coupling willtend to lead to a block copolymer product having less strength; theunlinked arms tend to dilute out the strength forming network in theblock copolymer A further problem with using lower Si/Li molar ratios isthat at high conversion it will tend to advance the coupling reaction tomake higher levels of 4-arm coupled product. The 4-arm coupled productis not preferred as it can contribute to excessive viscosity in the meltwhich makes melt processing of the product more difficult. Lower Si/Li(mol/mol) ratios are also not preferred because they can lead to weakerproducts that are more difficult to melt process.

On the other hand, Si/Li (mol/mol) ratios in excess of about 0.7 arealso not preferred. At Si/Li (mol/mol)=0.5, there is sufficient couplingagent present to couple all of the chain ends into a linear, 2-armproduct; this is the preferred result. Higher levels of Si/Li (mol/mol)only result in the addition of excess coupling agent. The addition ofexcess reagent contributes added cost to the process without anadvantage in the quality of the coupled polymer. At ratios greater thanabout 0.7, the excess coupling agent will tend to cap living chain endswithout linking them together; this will contribute to a decline incoupling efficiency at higher Si/Li molar ratios. Lower couplingefficiency will afford block copolymer products having less strength.The use of Si/Li (mol/mol) ratios in excess of about 0.7 willunnecessarily increase the cost of the process and will afford lowerquality coupled polymers.

As stated above, the coupling agent used in the present invention is analkoxy silane of the general formula R_(x)—Si—(OR′)_(y), where x is 0 or1, x+y=4, R and R′ are the same or different, R is selected from aryl,linear alkyl and branched alkyl hydrocarbon radicals, and R′ is selectedfrom linear and branched alkyl hydrocarbon radicals. The aryl radicalspreferably have from 6 to 12 carbon atoms. The alkyl radicals preferablyhave 1 to 12 carbon atoms, more preferably from 1 to 4 carbon atoms.Preferred tetra alkoxy silanes are tetramethoxy silane (“TMSi”),tetraethoxy silane (“TESi”), tetrabutoxy silane (“TBSi”), andtetrakis(2-ethylhexyloxy)silane (“TEHSi”). Preferred trialkoxy silanesare methyl trimethoxy silane (“MTMS”), methyl triethoxy silane (“MTES”),isobutyl trimethoxy silane (“IBTMO”) and phenyl trimethoxy silane(“PhTMO”). Of these the more preferred are tetraethoxy silane and methyltrimethoxy silane.

The temperature at which the coupling reaction is carried out can varyover a broad range and, for convenience, often is the same as thetemperature of polymerization. Although the temperature can vary broadlyfrom about 0° to 150° C., it will preferably be within the range fromabout 30° C. to 100° C., more preferably about 55° C. to about 80° C.

The coupling reaction is normally carried out by simply mixing thecoupling agent, neat or in solution, with the living polymer solution.The reaction period is usually quite short, and can be affected by themixing rate in the reactor. The normal duration of the coupling reactionwill be in the range of 1 minute to 1 hour. Longer coupling periods maybe required at lower temperatures.

After the coupling reaction, the linked polymers may be recovered, or ifdesired they may be subjected to a selective hydrogenation of the dieneportions of the polymer. Hydrogenation generally improves thermalstability, ultraviolet light stability, oxidative stability, andweatherability of the final polymer. It is important that the couplingagents not interfere with or otherwise “poison” the hydrogenationcatalyst.

Hydrogenation can be carried out via any of the several hydrogenation orselective hydrogenation processes known in the prior art. For example,such hydrogenation has been accomplished using methods such as thosetaught in, for example, U.S. Pat. Nos. 3,494,942; 3,634,594; 3,670,054;3,700,633; and Re. 27,145. These methods operate to hydrogenate polymerscontaining aromatic or ethylenic unsaturation, and are based uponoperation of a suitable catalyst. Such catalyst, or catalyst precursor,preferably comprises a Group VIII metal such as nickel or cobalt whichis combined with a suitable reducing agent such as an aluminum alkyl orhydride of a metal selected from Groups I-A, II-A and III-B of thePeriodic Table of the Elements, particularly lithium, magnesium oraluminum. This hydrogenation can be accomplished in a suitable solventor diluent at a temperature from about 20° C. to about 60° C., and apressure of about 2 bars to about 10 bars. Other catalysts that areuseful include titanium based catalyst systems and various heterogeneouscatalysts.

Hydrogenation can be carried out under such conditions that at leastabout 90 percent of the conjugated diene double bonds have been reduced,and between zero and 10 percent of the arene double bonds have beenreduced. Preferred ranges are at least about 95 percent of theconjugated diene double bonds have been reduced, and more preferablyabout 98 percent of the conjugated diene double bonds are reduced.Alternatively, it is possible to hydrogenate the polymer such thataromatic unsaturation is also reduced beyond the 10 percent levelmentioned above. In that case, the double bonds of both the conjugateddiene and arene may be reduced by 90 percent or more.

It has been found, as shown in the comparative example (7774 H2, Table4) in Example 1 below, that when employing tetramethoxy silane as thecoupling agent without passivation by the addition of alcohol, thepolymer tends to degrade on hydrogenation. The degradation appears to beby cleaving arms off at the Si coupling center. This could be reduced oreliminated by contacting the coupled polymer with an alcohol, such asmethanol, after coupling is complete and prior to hydrogenation. In thatcase it is preferred that the ratio of alcohol to P-Li be from about 1to 1.5 moles of alcohol per mole of P-Li (where the amount of P-Li inthe calculation is based on the amount of living chain ends which werepresent prior to the addition of the coupling agent). However, it hasbeen found that much less alcohol is needed when employing tetraethoxysilane or tetrabutoxy silane as the coupling agent. In that situationthe ratio of alcohol to P-Li should be from about 0.05 to about 0.5moles of alcohol per mole of P-Li. Likewise, when using trialkoxysilanes such as MTMS or IBTMO, it is preferable to add an alcohol, suchas 2-ethyl hexanol prior to hydrogenation. For example, the alcohol canbe added prior to hydrogenation at a ratio of alcohol to P-Li of about0.05 to about 0.5 moles of alcohol per mole of P-Li.

After hydrogenation, the hydrogenated polymers may be cleaned up bystandard techniques, such as addition of aqueous acid solutions toremove the residues of the polymerization initiator and hydrogenationcatalyst. It is usually preferred to add an antioxidant to the reactionmixture before isolation of polymer.

The polymer is separated from the reaction mixture by standardtechniques, such as steam stripping or coagulation with a suitablenon-solvent such as an alcohol or water. In the case of steam stripping,the polymer crumb may be separated from the volatile solvent bycountercurrent flow through a cyclone. In a like manner, the coagulatedpolymer crumb may be separated from the liquid solvent phase bycentrifugation or filtration. Alternatively, the polymer may berecovered by passing the cement through a devolatilizing extruder.Residual solvent and other volatiles can be removed from the isolatedpolymer by heating, optionally under reduced pressure or in a forcedairflow.

In accordance with a further embodiment of this invention, there isprovided a process for producing the polymers as defined above. Thisprocess includes basically three steps. The first step is the step inwhich a living polymer having the formula P-Li is produced. The secondstep is that in which this living polymer is coupled with the couplingagent of this invention as defined above. The third step, which isoptional, is a hydrogenation step.

The first step of this process is carried out by reacting amono-functional lithium initiator system with the respective monomer ormonomers to form the living polymer chain P-Li. This polymerization stepcan be carried out in one step or in a sequence of steps. In the casewhere the polymer chain P is a homopolymer or a random or taperedcopolymer of two or more monomers, the monomers are simultaneouslypolymerized with the lithium initiator. In the case where the polymerchain P is a block copolymer comprising two or more homo- or copolymerblocks, these individual blocks can be generated by incremental orsequential monomer addition.

The monomers that are generally employed, as well as the monomers thatare preferably used have been defined above in connection with the novelpolymers of this invention. These monomers are also preferred for theprocess of the present invention.

The lithium-based initiator systems used in the first step of theprocess to make the coupled polymers of this invention are based onlithium having the general formula R″ Li wherein R″ is a hydrocarbylradical of 1 to about 20 carbon atoms. Examples of such lithiuminitiators are methyllithium, isopropyllithium, n-butyllithium,sec-butyllithium, t-octyllithium, n-dodecyllithium, n-eicosyllithium,phenyllithium, naphthyllithium, p-tolyllithium, 4-phenylbutyllithium,cyclohexyllithium, and 4-cyclohexyllithium. The amount of the lithiuminitiator employed depends upon the desired properties of the polymer,particularly the desired molecular weight. Normally, theorganomonolithium initiator is employed in the range of from about 0.1to about 100 gram millimoles per 100 grams of total monomers.

The polymerization reaction is carried out in the presence of ahydrocarbon diluent. Preferably the hydrocarbon diluent is a paraffinic,cycloparaffinic or aromatic hydrocarbon having from 4 to 10 carbon atomsor a mixture of such diluents. Examples for the diluent are n-hexane,hexanes, n-heptane, heptanes, 2,2,4-trimethylpentane, cyclohexane,cyclopentane, isopentane, benzene and toluene. The reaction is generallycarried out with a weight ratio of diluent to monomers exceeding 1.Preferably the diluent is employed in a quantity of from about 200 toabout 1000 parts by weight per 100 parts by weight of total monomers.

It is also important to control the molecular weight of the variousblocks. Regarding the AB block copolymer composition, for each A blockthe desired block weights are 3,000 to about 60,000, preferably about5,000 to about 50,000. For each B block the desired block weights areabout 20,000 to about 200,000, preferably about 20,000 to about 150,000.These molecular weights are most accurately determined by lightscattering measurements, and are expressed as number average molecularweights.

Regarding the CDE block copolymer composition, for each D block thedesired block weights are 3,000 to about 60,000, preferably about 5,000to about 50,000. For each E block the desired block weights are about20,000 to about 200,000, preferably about 20,000 to about 150,000. Foreach C block the desired block weights are about 1,000 to about 25,000,preferably about 3,000 to about 15,000.

Regarding the FGH block copolymer composition, for each F block thedesired block weights are 3,000 to about 60,000, preferably about 5,000to about 50,000. For each G block the desired block weights are about10,000 to about 180,000. For each H block the desired block weights areabout 10,000 to about 180,000.

It is also important to control the microstructure or vinyl content ofthe conjugated diene in the B, C and E blocks. The term “vinyl” has beenused to describe the polymer product that is made when 1,3-butadiene ispolymerized via a 1,2-addition mechanism. The result is amonosubstituted olefin group pendant to the polymer backbone, a vinylgroup. In the case of anionic polymerization of isoprene, insertion ofthe isoprene via a 3,4-addition mechanism affords a geminal dialkyl C═Cmoiety pendant to the polymer backbone. The effects of 3,4-additionpolymerization of isoprene on the final properties of the blockcopolymer will be similar to those from 1,2-addition of butadiene. Whenreferring to the use of butadiene as the conjugated diene monomer, it ispreferred that about 10 to 80 mol percent of the condensed butadieneunits in the polymer block have a 1,2-addition configuration.Preferably, from about 30 to about 80 mol percent of the condensedbutadiene units should have 1,2-addition configuration. When referringto the use of isoprene as the conjugated diene, it is preferred thatabout 5 to 80 mol percent of the condensed isoprene units in the blockhave 3,4-addition configuration. Polymer microstructure (mode ofaddition of the conjugated diene) is effectively controlled by additionof an ether, such as diethyl ether, a diether, such as1,2-diethoxypropane, or an amine as a microstructure modifier to thediluent. Suitable ratios of microstructure modifier to lithium polymerchain end are disclosed and taught in U.S. Re. 27,145.

The polymerization reaction in step 1 usually occurs within a period oftime ranging from a few minutes up to about 6 hours. Preferably, thereaction is carried out within a time period of from about 10 minutes toabout 2 hours. The polymerization temperature is not critical and willgenerally be in the range of from 30° C. to about 100° C., preferably inthe range of about 55° to about 85° C.

At the conclusion of the polymerization, in order to carry out thesecond or coupling step, the polymerization mixture is blended with thecoupling agent. This is done before any material that would terminatethe polymerization reaction and that would remove the lithium atom fromthe polymer chain end is added to the reaction mixture. Thus theblending of the polymerization mixture and the coupling agent is carriedout before any material such as water, acid, or alcohol is added toinactivate the living polymer. The second step of coupling the livingpolymer is thus carried out as described in detail above. The third stepis the hydrogenation, which is also described in detail above.

The relative amounts of the tetra-branched (IV), tri-branched (II),di-branched (II) and linear diblock (I) species are: 0 to 5 weightpercent tetra-branched IV, 0 to 60 weight percent tri-branched III, 40to 95 weight percent di-branched II and 2 to 10 weight percent lineardiblock I. Preferred amounts are: 0 to 5 weight percent IV, 0 to 36weight percent III, 60 to 95 weight percent II and 4 to 8 weight percentI.

The block copolymer composition has a Coupling Efficiency (“CE”) ofabout 90 to 98 weight percent, preferably about 92 to about 98 weightpercent. Coupling Efficiency is defined as the proportion of polymerchain ends which were living, P-Li, at the time the coupling agent wasadded that are linked via the residue of the coupling agent at thecompletion of the coupling reaction. In practice, Gel PermeationChromatography (GPC) data is used to calculate the coupling efficiencyfor a polymer product. The sum of the areas under the GPC curve for allof the coupled species (II+III+IV) is divided by the sum of the areasunder the GPC curve for all of the coupled moieties plus the area underthe curve for the starting, uncoupled polymer species (I+II+III+IV).This ratio is multiplied by 100 to convert the coupling efficiency to apercentage value.

The percentage of mono alkenyl blocks (i.e., A blocks in the ABcopolymer, D blocks in the CDE copolymer, and F blocks in the FGHcopolymer) in the block copolymer composition is desired to be about 5to about 50 weight percent, preferably about 10 to about 40 weightpercent.

Various materials are known to be detrimental to the lithium alkylinitiated polymerization. Particularly, the presence of carbon dioxide,oxygen, water and alcohols should be avoided during anorganomonolithium-initiated polymerization reaction of step 1 of thiscombined process for making the coupled polymers. Therefore, it isgenerally preferred that the reactants, initiators, and the equipment befree of these materials and that the reaction is carried out under aninert gas such as nitrogen.

In one embodiment of the present invention, one may polymerize firststyrene, then butadiene and finally isoprene, therein producing anS-B-I-triblock arm. As shown below in Example 5, use of isoprene to capthe arm results in high coupling efficiencies and increased linearity ofthe polymer.

EXAMPLES

The following examples are provided to illustrate the present invention.The examples are not intended to limit the scope of the presentinvention and they should not be so interpreted. Amounts are in weightparts or weight percentages unless otherwise indicated.

Example 1

A diblock polymer anion, S-B-Li, is prepared as follows (Experiment7774): 96 kg cyclohexane and 24 kg styrene are charged to a reactor,followed by 590 milliliters of a sec-butyl lithium solution (12% wtBuLi, 0.86 mol). A second reactor is charged with 264 kg cyclohexane, 25kg diethyl ether and 20.2 kg butadiene. Following titration to removeimpurities, 95 kg of polystyryllithium solution prepared in the firstreactor is transferred to the second reactor. After polymerization hascommenced, an additional 20.3 kg of butadiene is added, at a ratesufficient to keep the temperature around 55° C. After about 98%conversion of the butadiene, 45 grams of tetramethoxy silane (“TMSi”) isadded (TMSi:PLi about 0.45). The final product consists of an almost50:50 mixture of 2-arm (linear) and 3-arm polymer, with an overallcoupling efficiency (all coupled products/coupled products+un-coupleddiblock) of 95.3% as measured by a Gel Permeation Chromatography (GPC)method. Before coupling, the styrene block has a molecular weight of29,000 and the butadiene block has a molecular weight of 62,000.

An aliquot of this polymer is passivated prior to hydrogenation by theaddition of MeOH. An equivalent of MeOH is added for every equivalent ofC-Li chain ends present prior to the coupling reaction. The MeOHpassivated cement is hydrogenated using a standard Co/Al technique. Thehydrogenation catalyst is prepared by adding triethylaluminum to cobalt(II) neodecanoate (Al/Co=2.0 (mol/mol)) in a hydrocarbon solvent. Thecatalyst is added to the cement under hydrogen pressure at a level thataffords a concentration of 6 ppm of Co in the cement. Hydrogenation at78° C. for 18 hours results in the saturation of 98.5% of the C═C bondsin the rubber segment of the polymer (see Experiment 7774H3 in Table 4).Importantly, after complete hydrogenation, the coupling efficiency ofthe polymer is unchanged; the coupling efficiency of the hydrogenatedpolymer is assayed at 95.7% by the GPC method. The catalyst is removedby washing with aqueous phosphoric acid and water, and the polymer isrecovered via steam stripping, under conditions typical for hydrogenatedpolymers.

In a comparative example, a sample of the same polymer (7774) ishydrogenated without methanol addition (Experiment 7774H2, see Table 4)using the Co/Al technique ([Co]=16 ppm, 60° C., 6 hr). At 99.5%hydrogenation of the C═C centers, the cement which has not beenpassivated with MeOH has undergone severe degradation by a chaincleavage mechanism; only 90.6% of the polymer remains coupled as assayedby GPC. Nearly 5% of the coupled polymer in the starting material hasbeen degraded to the strength reducing uncoupled diblock arm duringhydrogenation. Hydrogenation without passivation with MeOH results indegradation of the coupled polymer.

In a second comparative example, a sample of the same polymer (7774) ishydrogenated without methanol addition (Experiment 7774H1, see Table 3)using a standard Ni/Al technique. The hydrogenation catalyst is preparedby adding triethylaluminum to nickel(II) octoate (Al/Ni=2.16 (mol/mol))in a hydrocarbon solvent. The catalyst is added to the cement underhydrogen pressure at a level that affords a concentration of 45 ppm ofNi in the cement. Hydrogenation at 100° C. for 18 hours results in thesaturation of 97.1% of the C═C bonds in the rubber segment of thepolymer. At this level of conversion, the cement that has not beenpassivated with MeOH has been severely degraded; only 89.8% of thepolymer remained coupled following hydrogenation. Over 5% of the coupledpolymer in the starting material has been degraded to the strengthreducing uncoupled diblock arm during hydrogenation. Hydrogenationwithout passivation with MeOH results in degradation of the coupledpolymer.

The average mechanical properties of oiled compounds prepared from thepolymer hydrogenated in the presence of methanol (CE=95.7% afterhydrogenation) are compared to those of the same compounds, but preparedwith an S-EB-S sequentially polymerized triblock copolymer (listed asCP-1), in Table 1 below. The properties of the compounds made with thecoupled product of the present invention are quite comparable to thoseof the compounds made with the sequential triblock.

TABLE 1 Average Mechanical Properties Of Oiled Compounds Prepared FromThe Polymer Hydrogenated In The Presence Of Methanol Tensile 100% 500%1000% 1500% Strength Elongation Modulus Modulus Modulus Modulus polymerphr oil (PSI) (%) (PSI) (PSI) (PSI) (PSI) CP-1 200 954 1845 16 4 134 391CP-1 300 469 1973 8 23 74 172 CP-1 500 237 2176 3 9 25 76 7774H3 200 8121788 14 43 132 412 7774H3 300 424 2026 — 13 55 153 7774H3 500 190 2011 26 26 98

Table 2 summarizes the results of subsequent reactions in which diblockcopolymers comparable to those prepared in Experiment 7774 above(Example #1) are coupled with TMSi at TMSi:Li=0.45 (mol/mol). Goodcoupling efficiency is observed. This coupling technique is quiterobust.

TABLE 2 Results for S-Bd-Li Coupling Using Tetramethoxysilane BlockMolecular Weight Si/Li CE Vinyl Arm Distribution % Expt. Step I Step II(mol/mol) (%) (%) 1 2 3 4 7774 28.3 59.0 0.45 95.2 38 5 46 49 t 779228.2 61.2 0.45 95.9 38 4 51 43 2 7800 28.2 64.1 0.45 93.2 38 7 45 46 2“Block Molecular Weight” values are in thousands, “Si/Li” is the ratioof tetramethoxysilane coupling agent to s-BuLi initiator, “CE” iscoupling efficiency, Vinyl refers to the 1,2-content of the butadieneportion of the polymer, 1 Arm is uncoupled diblock (I), 2 Arm is thelinear triblock copolymer (II), 3 (III), and 4 Arm (IV) polymers areradial in structure, and t stands for a trace.

For all polymerizations, half of the butadiene in Step II is added inbatch with the remainder being added via a programmed addition. Allpolymerizations are at 14% solids. The coupling agent is added at 6half-lives into Step II.

The results of hydrogenation using Ni and Co based catalysts aresummarized in Tables 3 and 4, respectively. All of the hydrogenationreactions described in Table 3 are comparative examples. All areperformed without methanol addition and show severe loss of couplingefficiency following hydrogenation.

TABLE 3 Results For Hydrogenation Using A Ni/Al Technique, Without MeOHPassivation, Of S-Bd-S Polymers Coupled With TetramethoxysilaneHydrogenation Results Hydrogenation Conditions RU [Ni] Temp. Time (meq/CONVERSION CE Expt. (ppm) (° C.) (hr) g) (%) (% wt) 7774H1 45 100 180.35 97.1 89.8 7776H1 50 85 19 0.11 99.1 83.3 “[Ni]” is the finalconcentration of Ni in the polymer cement, the Ni is from a standardnickel octoate/triethylaluminum (Al/Ni = 2.16 (mol/mol)) catalyst,“Temp.” is the final hydrogenation temperature, “Time” is the timerequired to reach the final level of conversion, “RU” is the residualunsaturation of the final polymer as measured by H-NMR and is reportedin meq of C═C centers per g of polymer, “Conversion” is the final levelof saturation of the butadiene portion of the polymer and “CE” is ameasure of the level of coupling in the final, hydrogenated polymer.Before hydrogenation, over 92 wt % of the 7776 product was linked by thecoupling agent.

Experiment 7774H2 in Table 4 is a comparative example; it is conductedwithout passivating the cement with MeOH before hydrogenation. As notedabove, the polymer is severely degraded during hydrogenation, as aresult the other examples in Table 4 are illustrative embodiments of thepresent invention. In each of these experiments, the cement ispassivated by the addition of an equivalent of MeOH prior tohydrogenation. It should be noted that by comparison to the couplingefficiency of the corresponding starting polymer in Table 2 the couplingefficiency of the hydrogenated polymer is hardly changed. When TMSi isused as the coupling agent, passivation of the cement by the addition ofan equivalent of MeOH prior to hydrogenation is an effective way toprepare highly coupled and as a result very strong block copolymers.

TABLE 4 Results For Hydrogenation Using A Co/Al Technique Of S-Bd-SPolymers Coupled With Tetramethoxysilane Hydrogenation ResultsHydrogenation Conditions RU [Co] Temp. Time (meq/ CONVERSION CE Expt.(ppm) (° C.) (hr) g) (%) (% wt) 7774H2 16.0 60 6 0.06 99.5  90.6* 7774H36.0 78 18 0.18 98.5 95.7 7776H2 9.0 92 28 0.14 99.4 92.1 7779H2 5.5 72 10.06 99.5 88.7 7792H1 5.5 65 19 0.09 99.2 94.9 7792H2 5.5 60 24 0.0399.7 95.1 7800 4.0 87 18 0.14 98.8 91.8 *(w/o MeOH) “[Co]” is the finalconcentration of Co in the polymer cement, the Co is from a standardcobalt neodecanoate/triethylaluminum (Al/Co = 2.0 (mol/mol)) catalyst,“Temp.” is the final hydrogenation temperature, “Time” is the timerequired to reach the final level of conversion, “RU” is the residualunsaturation of the final polymer as measured by H-NMR and is reportedin meq of C═C centers per g of polymer, “Conversion” is the final levelof saturation of the butadiene portion of the polymer and “CE” is ameasure of the level of coupling in the final, hydrogenated polymer. Allhydrogenation experiments, except for Run 7774 w/o MeOH, involvedtreatment of the polymer cement with an equivalent (basis C—Li centersin the uncoupled polymer) of MeOH prior to hydrogenation. Prior tohydrogenation, 89 wt % of the 7779 product was linked by the couplingagent.

Using the polymer synthesis procedure outlined above in Example 1, aliving triblock copolymer, Bd-S-Bd-Li, is prepared. An aliquot of theliving polymer is terminated at each step in the polymerization by theaddition of MeOH and the individual aliquots are analyzed by GPCaffording the step block molecular weight results shown in Table 5. Theliving cement is coupled using TMSi as the coupling agent (TMSi/LivingChain End=0.45 (mol/mol)). The efficiency of the coupling reaction isexcellent, 96%, as is seen for the coupling of living diblockcopolymers. As displayed in Table 5, the coupled polymer consists ofmostly a linear dimer and a branched three arm polymer as is observedfor the coupling of living diblock copolymers. The new polymer has thepentablock configuration Bd-S-Bd-S-Bd.

TABLE 5 Results for Bd-S-Bd-Li Coupling Using Tetramethoxysilane. BlockMolecular Arm Distribution Weight Si/Li CE Vinyl (%) Expt. Step I StepII Step III (mol/mol) (%) Step I Step III 1 2 3 4 7768 5.9 8.9 26.5 0.4595 30 38 5 51 40 4 See footnote to Table 2 for a definition of thecolumn headings.

The tetramethoxysilane coupled, pentablock copolymer cement fromExperiment 7768 is passivated by the addition of one mole of MeOH forevery mole of living chain ends present in the cement prior to thecoupling reaction. Hydrogenation, after passivation with MeOH, using theNi/Al technique described in Table 6, affords a selectively hydrogenatedpentablock copolymer with essentially no loss of coupling efficiency inthe saturated polymer. The hydrogenation catalyst is extracted from thepolymer cement by contacting the cement with aqueous acid in thepresence of air. The polymer is recovered from the washed cement by asteam stripping process. Analysis of the product afforded the data inTable 6. A solvent cast film of the product polymer has remarkablestrength. In this illustrative embodiment of the present invention, astrong, highly coupled E/B-S-E/B-S-E/B polymer is prepared by 1)coupling the living triblock copolymer with tetramethoxysilane, 2)passivating the cement by the addition of MeOH, and 3) hydrogenating thepolymer using a Ni/Al technique.

TABLE 6 Results for Hydrogenation of Bd-S-Bd-S-Bd Polymer Coupled WithTetramethoxysilane. Hydrogenation Conditions Hydrogenation Conditions[Ni] Temp. Time RU Conversion CE Expt. (ppm) (° C.) (hr) (meq/g) (%) (%wt) 7768H1 60 70 75 0.19 98.6 95.0 See footnote to Table 3 for adefinition of the column headings.

Example 2

A diblock polymer anion, S-B-Li, is prepared as follows (run 7852D): 60kg cyclohexane and 15 kg styrene are charged to a reactor, followed by400 milliliters of sec-butyl lithium. A second reactor is charged with155.4 kg cyclohexane, 15 kg diethyl ether and 23.8 kg butadiene.Following titration to remove impurities, 56 kg of polystyryllithiumsolution prepared in the first reactor is transferred to the secondreactor. After about 98% conversion of the butadiene, 26.3 grams oftetramethoxy silane (“TMSi”) is added (TMSi:PLi about 0.45). The finalproduct consists of 41% 2-arm (linear) and 53% 3-arm polymer, with anoverall coupling efficiency (all coupled products/coupledproducts+un-coupled diblock) of about 96%. The styrene block has amolecular weight of 29,300 and the butadiene block has a molecularweight of 62,000.

The results of the following hydrogenation experiments are summarized inFIG. 1.

A sample of the polymer is hydrogenated with 100% methanol/Li addition(run 7852D-H4) to a residual olefin concentration of 0.10 meq./g. in thepresence of 10 ppm Co/solution of a cobalt neodecanoate-aluminumtriethyl catalyst (Al/Co=1.6 mol/mol). After hydrogenation under theseconditions, the polymer remains 95.7% coupled. The catalyst is removedby washing with aqueous phosphoric acid, and the polymer is recoveredvia steam stripping, under conditions typical for hydrogenated polymers.

A sample of the polymer is hydrogenated with 50% methanol/Li addition(run 7852D-H2) to a residual olefin concentration of 0.07 meq/g in thepresence of 10 ppm Co/solution of a cobalt neodecanoate-aluminumtriethyl catalyst (Al/Co=1.6 mol/mol). After hydrogenation under theseconditions, the polymer remains 94.7% coupled. The catalyst is removedby washing with aqueous phosphoric acid, and the polymer is recoveredvia steam stripping, under conditions typical for hydrogenated polymers.

A sample of the polymer is hydrogenated with 10% methanol/Li addition(run 7852D-H1) to a residual olefin concentration of 0.13 meq/g in thepresence of 16 ppm Co/solution of a cobalt neodecanoate-aluminumtriethyl catalyst (Al/Co=1.6 mol/mol). After hydrogenation under theseconditions, the polymer remains 92% coupled. The catalyst is removed bywashing with aqueous phosphoric acid, and the polymer is recovered viasteam stripping, under conditions typical for hydrogenated polymers.

A diblock polymer anion, S-B-Li, is prepared as follows (run 7919D): 80kg cyclohexane and 20 kg styrene are charged to a reactor, followed by510 milliliters of sec-butyl lithium. A second reactor is charged with188 kg cyclohexane, 18 kg diethyl ether, and 28.5 kg butadiene.Following titration to remove impurities, 67 kg of polystyryllithiumsolution prepared in the first reactor is transferred to the secondreactor. After about 98% conversion of the butadiene, 43.3 grams oftetraethoxy silane (“TESi”) is added (TESi:PLi about 0.45). The finalproduct consists of 54.5% 2-arm (linear) and 38.6% 3-arm polymer, withan overall coupling efficiency (all coupled products/coupledproducts+un-coupled diblock) of about 96%. The styrene block has amolecular weight af 28,730 and the butadiene block has a molecularweight of 62,000.

A sample of the polymer is hydrogenated with 10% methanol/Li addition(run 7919D-H1) to a residual olefin concentration of 0.21 meq/g in thepresence of 5 ppm Co/solution of a cobalt neodecanoate-aluminum triethylcatalyst (Al/Co=1.6 mol/mol). After hydrogenation under theseconditions, the polymer remains 94.4% coupled. The catalyst is removedby washing with aqueous phosphoric acid, and the polymer is recoveredvia steam stripping, under conditions typical for hydrogenated polymers.

Comparative Example 1 (Experiment 167)

When a trialkoxysilane hydride is used as a coupling agent, rather thanthe tetraalkoxysilanes of the present invention, the coupled polymersuffers extreme degradation during hydrogenation. A solution of aliving, anionic polybutadienyl-lithium reagent is prepared by adding24.52 g of a 10% wt solution of s-BuLi (0.038 mol) to a mixturecontaining 200 g of butadiene, 121 g of diethyl ether, and 1655 g ofcyclohexane. Polymerization is allowed to proceed for 32 minutes attemperatures below 55° C. (10 half-lives). An aliquot of the polymer isquenched and analyzed by GPC. The molecular weight of the polybutadieneis 4,802. The remainder of the living polybutadienyl-lithium cement istreated with 1.69 g of trimethoxysiliconhydride, (MeO)₃SiH, TMSiH(0.0138 mol) (Si/Li=0.36 (mol/mol). The coupling reaction is allowed toproceed at 40° C. for 30 minutes. An aliquot of the coupled cement isanalyzed by GPC and found to contain only three arm branched polymer anduncoupled homopolymer. The coupling efficiency is 84%. The cement istreated with 1.4 g of MeOH (0.04 mol); this is one mole of MeOH per C-Lichain end in the living polymer prior to coupling. Whentetramethoxysilane is used as a coupling agent, this is enough MeOH topassivate the polymer cement against degradation during hydrogenation ofthe polybutadiene. Hydrogenation, using the Ni/Al catalyst (101 ppm ofNi in the cement) described in Table 3, at 700 psi of hydrogen pressure,at temperatures below 70° C. for 3 hr, results in complete saturation ofthe butadiene polymer (99.5% of the C═C centers is reduced).Unfortunately, degradation of the coupled polymer is extreme. The GPCanalysis of the hydrogenated polymer is so complex due to thefragmentation of the polymer that quantitative analysis is not possible.It is clear that most of the coupled polymer degraded duringhydrogenation. In this case, using the MeOH passivation technique thathas worked to protect tetramethoxysilane coupled polymers fromdegradation during hydrogenation and using the same Ni/Al hydrogenationtechnique does not work when the polymer is coupled with TMSiH.

Comparative Example 2 (Experiment 155)

The procedure of Comparative Example #1 is repeated with the significantexception that triethoxysiliconhydride, (EtO)₃SiH, TESiH, is used as thecoupling agent rather than TMSiH. Hydrogenation with a Ni/Al techniquegave extreme degradation, which has not been observed whentetraethoxysilane, TESi, is used as the coupling agent. Addition of anequivalent of MeOH before hydrogenation does not passivate the polymeragainst degradation as is observed when tetramethoxysilane is used asthe coupling agent. When TESiH is used to couple apolybutadienyl-lithium reagent and an equivalent of MeOH is added beforehydrogenation extreme degradation of the coupled polymer duringhydrogenation is still observed.

In this preparation, the living, anionic polybutadienyl-lithium moietyhas a molecular weight of 5,240 (by GPC analysis of a terminatedaliquot). The living polymer cement is treated with sufficient TESiH togive a Si/Li ratio of 0.45 mol/mol. Analysis of the coupled polymer (byGPC) shows essentially complete conversion to the branched three armpolymer; the level of uncoupled arms is estimated to be less than 3%.The efficiency of the coupling reaction is excellent. Half of thecoupled polymer cement is carried forward to be hydrogenated using theNi/Al procedure described in Comparative Example 1. The hydrogenatedpolymer product is washed with aqueous acid to remove the spenthydrogenation catalyst and analyzed by GPC. Over half of the coupledpolymer product is degraded to a species having a molecular weightcomparable to that of the starting uncoupled polymer chain (arm). Asnoted in Comparative Example 1, this sample is so badly degraded that itis not possible to quantitatively measure the level of degradation fromthe GPC data. Clearly, the process that uses TESiH as the coupling agentdoes not give the results which are observed when TESi is used as thecoupling agent. The polymer coupled with the triethoxysilane reagent isbadly degraded during hydrogenation and is not an example of the presentinvention.

The remainder of the coupled, but not hydrogenated, polymer cement istreated with one equivalent of MeOH per equivalent of C-Li centers inthe uncoupled precursor cement. The MeOH treated cement is thenhydrogenated using the procedure described above for the “not MeOHtreated” cement. Analysis by GPC shows even more extreme degradation inthis sample. More than 70% of the coupled polymer is degraded tomaterial having a molecular weight similar to that of an unlinked arm.Clearly, adding MeOH to the TESiH coupled polymer prior to hydrogenationdoes not passivate this product to degradation during hydrogenation.When tetramethoxysilane is used as the coupling agent, as outlined inExample 1, added MeOH did passivate the polymer against degradationduring hydrogenation. A process that uses triethoxysiliconhydride as thecoupling agent with alcohol addition prior to hydrogenation is not partof the present invention.

Comparative Example 3

A living, anionic, polystyrene-polybutadienyl-lithium reagent is coupledwith methyldichlorosiliconhydride, MeCl2SiH, and MDSiH. Hydrogenation ofthe coupled polymer cement using the Ni/Al technique described in Table3 results in degradation of the coupled polymer ranging from 10 to 90%.From severe to extreme degradation during hydrogenation is observed whenMDSiH is used as the coupling agent. This coupling agent is not part ofthe present invention.

Example 3

A series of laboratory screening experiments are executed to determinethe effect of tetramethoxysilane (TMSi) to Li ratio on overall couplingefficiency and arm distribution.

Polybutadienyllithium of a nominal molecular weight of 2,500 is preparedas follows: 750 grams of cyclohexane, 60 grams of diethyl ether and 100grams of butadiene are charged to a 1-liter Buchi glass autoclave. Thereactor is heated to about 40° C. and about 21 grams of butyllithiumsolution is added. The reaction temperature is adjusted to about 50° C.and the reaction is allowed to proceed to about 99% conversion. In thefirst example, a solution of TMSi in cyclohexane is added at about 1.6mL/min using a syringe pump. Enough TMSi is added to provide 0.5 molesTMSi per mole polymer-Li at the end of the program. Under theseconditions, it is anticipated that the coupling reagent will react asfast as it is added, to give close to the maximum attainable couplingefficiency. The result (Table 7) demonstrates that coupling efficienciesin excess of 90% may be achieved. The entire TMSi charge is addedrapidly in the remaining examples. High coupling efficiencies areobtained, even in the presence high levels of TMSi, and the fraction ofradial (>2 arm) product is much lower.

TABLE 7 Coupling Efficiencies Linear Run # TMSi:Pli CE Un-cpl'd (2-arm)3-arm 4-arm 3-1  0.3¹ 93% 7%  3% 57% 32%  3-2 0.5 95% 5% 76% 17% 2% 3-30.7 92% 8% 72% 18% 2% ¹Total Charge of 0.5:1 TMSi:PLi over 20 minutes. Aratio of 0.3 corresponds to the observed arm distribution.

Example 4

A series of laboratory screening experiments were executed to determinethe effect of the tetraethoxysilane (TESi) to Li ratio and the presenceof polar co solvents and modifiers on overall coupling efficiency andarm distribution in coupling reactions of polyisoprenyllithium.Reactions were carried out according to the following general procedure;details for individual reactions are summarized in Table 8. Cyclohexane(CH) and any co-solvents used in the process were charged into a 1-literstainless steel autoclave and the temperature was increased to 40° C.The s-butyllithium solution (about 5% wt in CH) was then charged,followed immediately by the batch portion of the isoprene charge, andthe temperature was increased to 50° C. Consumption of the isoprenemonomer was monitored in real-time. After about half of the batch chargehad been consumed, the remainder of the isoprene was added at a rate of0.5 cc/min. When the polymerization was judged to be complete, the TESiwas added as a 10% wt. solution in cyclohexane. Reaction was allowed tocontinue for 1 hour at 50° C., although intermediate samples suggestthat the coupling reactions were generally complete in 15 minutes. Themolecular weight of the initial arm, as well as the overall couplingefficiency and the distribution of arms, were determined by GelPermeation Chromatography. ¹H NMR determined the isoprene microstructureand the polymer concentration (solids). The moles ofpolyisoprenyllithium were calculated using the molecular weights andsolids values from these analyses. This data is summarized in Table 9.It is apparent that coupling efficiencies on the order of 90% can beobtained when the molar ratio of TESi to lithium is close to 0.5, andthat the product is substantially linear. In contrast, almost 30% of thecoupled species were radial (≧3-arms) when a similar experiment wasperformed using polybutadienyllithium. These results were observed inthe presence of both diethyl ether and diethoxypropane (DEP), indicatingthat the coupling reaction is not very sensitive to the solvent system.

TABLE 8 s-buLi TESi Run CH soln. soln. # (g) (g) Modifier (#g) Ip Batch(g) Ip Prog. (g) 1 348 25.3 none 53.1 9.4 13.1 2 360 13.5 none 53.1 9.413.1 3 358 16.2 none 53.1 9.4 13.1 4 308 27.9 diethyl ether (38) 53.19.4 13.1 5 316 20.2 diethyl ether (38) 53.1 9.4 13.1 6 311 25.3 diethylether (38) 53.1 9.4 13.1 7 312 16.2 DEP(2.1)¹ 53.1 9.4 11.8¹Diethoxypropane, 10% wt. in cyclohexane.

TABLE 9 Sol- Un- Linear Radial Coupling Run MW ids TESi: % 3,4 cou- (2-(3- Effi- # p(Ip) (wt) Li Isop. pled arm) arm) ciency 1 3,600 8.5% 0.31 8% 31% 46% 23%   69% 2 8,400 8.3% 0.74  8% 52% 49% 0%¹ 48% 3 6,500 8.9%0.48  8% 12% 88% 0%¹ 88% 4 5,000 9.5% 0.38 40% 10% 90% 0%¹ 90% 5 8,7008.2% 0.78 40% 55% 44% 2%  45% 6 6,200 8.4% 0.55 40% 23% 77% 0%¹ 77% 76,300 9.0% 0.50 10% 11% 89% 0%¹ 89% ¹Small high MW shoulder, estimatedto be no more than 10% of the area of the linear peak.

Example 5

The addition of a small amount of isoprene at the end of the dienepolymerization allows the production of a highly coupled, primarilylinear polymer comprised essentially of butadiene and styrene, asdemonstrated by the following example.

A 2-gallon stainless steel reactor was charged with 3.2 kg ofcyclohexane, 240 g of diethyl ether, and 107 g, of styrene. The reactortemperature was increased to about 50° C. Impurities were removed byadding small aliquots of s-butyllithium until the first evidence ofcolor. 25.3 milliliters of a solution of an approximately 6% wt solutionof s-butyllithium in cyclohexane was added, and the styrene was allowedto complete polymerization at 50° C.–60° C. The molecular weight of thepolystyrene produced in this reaction was determined to be 6,300 AMU byGPC. The temperature was adjusted to 50° C. and 710 g of butadiene wereadded at such a rate as to allow the temperature to remain about 50° C.When the butadiene polymerization was complete, 10 g of isoprene wasadded. A sample collected at this point had a styrene content of 13.8%wt and a vinyl content of 39% basis ¹H NMR and an overall molecularweight of 50,800 as determined by GPC. After the isoprene had reactedfor about 10 minutes, 1.88 g of TESi were added, and the couplingreaction was allowed to proceed for 60 minutes at 50° C. Methanol (0.6 gas a 10% wt solution in CH, one mole per mole of Li) was added toterminate any uncoupled chains the following morning. The final producthad a coupling efficiency of 90%, and 87% of the coupled species werelinear, the remaining being 3-arm radial.

The polymer prepared above was hydrogenated using a standard Ni/Altechnique. The hydrogenation catalyst was prepared by addingtriethylaluminum to nickel(II) octoate in a 2.16 to 1 molar ratio(Al/Ni=2.16 (mol/mol)) in a hydrocarbon solvent. The catalyst was addedto the cement under hydrogen pressure (700–800 PSI) in three 20milliliter aliquots, affording a final concentration of about 75 ppm ofNi in the cement. The initial aliquot was charged at a temperature ofabout 50° C. and the temperature was allowed to increase to about 60° C.The second aliquot was added after about 2 hours. About 5 hours later,the temperature was increased to 80° C. and the third aliquot was added.The hydrogenation reaction was allowed to proceed overnight, resultingin the saturation of about 99% of the C═C bonds in the rubber segment ofthe polymer. The catalyst was removed by washing with aqueous phosphoricacid and water, antioxidant (Ethanox 330, 0.1 PHR) was added, and thepolymer was recovered via steam stripping, under conditions typical forhydrogenated polymers. The final product maintained a couplingefficiency of 90% with 87% of the coupled product being linear.

Example 6

A diblock polymer anion, S-B-Li, is prepared as follows: 360 kg ofcyclohexane and 19.7 kg, of styrene were charged to a reactor. Thereactor temperature was increased to about 40° C. Impurities wereremoved by adding small aliquots of s-butyllithium until the firstevidence of color. 1,820 milliliters of a solution of an approximately12% wt solution of s-butyllithium in cyclohexane was added, and thestyrene was allowed to complete polymerization at about 60° C. Themolecular weight of the polystyrene produced in this reaction wasdetermined to be 7,900 AMU by GPC. The temperature was maintained at 60°C., 333 g. of 1,2-diethoxypropane were added, and then 70.4 kg ofbutadiene were added at such a rate as to allow the temperature toremain about 60° C. A sample collected at this point had a styrenecontent of 25% wt and a vinyl content of 69% basis ¹H NMR and an overallmolecular weight of 34,700 as determined by GPC. 251 g of TESi wasadded, and the coupling reaction was allowed to proceed for 60 minutesat 60° C. Methanol (8.1 g, 0.1 mole per mole of Li) was added toterminate the reaction. The final product had a coupling efficiency of91%, and 66% of the coupled species were linear, the remaining being3-arm radial.

A sample of the polymer was hydrogenated to a residual olefinconcentration of 0.13 meq/g in the presence of 15 ppm Co/solution of acobalt neodecanoate-aluminum triethyl catalyst (Al/Co=1.7 mol/mol).After hydrogenation under these conditions, the polymer remains 91%coupled. The catalyst is removed by washing with aqueous phosphoricacid, and the polymer is recovered via steam stripping, under conditionstypical for hydrogenated polymers.

Example 7

A diblock polymer anion, S-B-Li, is prepared as described in Example 6:361 kg of cyclohexane and 16.7 kg, of styrene were charged to a reactor.The reactor temperature was increased to about 40° C. Impurities wereremoved by adding small aliquots of s-butyllithium until the firstevidence of color. 1,900 milliliters of a solution of an approximately12% wt solution of s-butyllithium in cyclohexane was added, and thestyrene was allowed to complete polymerization at about 60° C. Themolecular weight of the polystyrene produced in this reaction wasdetermined to be 6,400 AMU by GPC. The temperature was maintained at 60°C., 320 g. of 1,2-diethoxypropane were added, and then 72.6 kg ofbutadiene were added at such a rate as to allow the temperature toremain about 60° C. A sample collected at the end of the butadienepolymerization had a styrene content of 21.3% wt and a vinyl content of69% basis ¹H NMR and an overall molecular weight of 35,000 as determinedby GPC. Following polymerization of the majority of the butadiene, 623g. of isoprene was added. The isoprene was allowed to polymerize, andthen 257 g of TESi was added, and the coupling reaction was allowed toproceed for 60 minutes at 60° C. Methanol (8.5 g, 0.1 mol per mol of Li)was added to terminate the reaction. The final product had a couplingefficiency of 91%, and 72% of the coupled species were linear, theremaining being 3-arm radial.

A sample of the polymer was hydrogenated to a residual olefinconcentration of 0.09 meq/g in the presence of 20 ppm Co/solution of acobalt neodecanoate-aluminum triethyl catalyst (Al/Co=1.7 mol/mol).After hydrogenation under these conditions, the polymer remained 91%coupled. The catalyst was removed by washing with aqueous phosphoricacid, and the polymer was recovered via steam stripping, underconditions typical for hydrogenated polymers.

Example 8

In Example 8, a number of selectively hydrogenated styrene/butadieneblock copolymers were prepared with a variety of coupling agentsaccording to a standard polymerization recipe. The molecular parametersof the desired polymer is shown below in Table 10, where Step 1 is thepolystyrene block (A), SD1 apparent is the styrene equivalent molecularweight of the styrene/butadiene diblock arm (P), and CE is couplingefficiency. Coupling Efficiency is defined as the proportion of polymerchain ends which were living, P-Li, at the time the coupling agent wasadded that are now linked via the residue of the coupling agent at thecompletion of the coupling reaction. In practice, Gel PermeationChromatography (GPC) data is used to calculate the coupling efficiencyfor a polymer product. The sum of the areas under the GPC curve for allof the coupled species (II+III+IV) is divided by the sum of the areasunder the GPC curve for all of the coupled plus the area under the curvefor the starting, uncoupled polymer species (I+II+III+IV). This ratio ismultiplied by 100 to convert the coupling efficiency to a percentagevalue.

TABLE 10 Starting recipe for the syntheses described in Example 8.Target Polymer Step I (kg/mole) 29.0 SD1 Mw (kg/mole) apparent 136 PSC(%) 33 Vinyl content (%) 40

The butadiene polymerization was started at 70° C. and the temperaturewas raised adiabatically up to 80° C. After the butadiene addition wasstopped, a soak time of 5 minutes was maintained. Following that thecoupling agent was added and allowed to react for at least 10 minutesbefore the polymer cement was sampled.

The following coupling agents were used in the polymerizations:

-   Trimethoxy silane hydride (TMS)-   Methyl trimethoxy silane (MTMS)-   Octyl trimethoxy silane (OCTMO)-   Isobutyl trimethoxy silane (IBTMO)-   Tetrakis 2-butoxyethyl orthosilicate (BG).-   Tetrabutoxy orthosilicate (TBS)

The results of the polymerization experiments are shown below in Table11, where percentages are expressed as weight percent, CA is couplingagent, CA/Li is the molar ratio of coupling agent to lithium, the 4-arm(IV) fraction may contain a small amount of high molecular weightpolymer (it is higher in MW than the tetrabranched polymer (IV), and maycome from the coupling of Si centers via an etherification reaction(Si—O—Si); these polymers were included as coupled product in thecalculation of coupling efficiency), PSC is percent styrene in theentire block copolymer, and Vinyl is the 1,2 content of the butadieneblocks:

TABLE 11 Run # 8-1 8-2 8-3 8-4 8-5 8-6 CA TMS BG OCTMO MTMS IBTMO TBSCA/Li 0.5 0.5 0.5 0.5 0.5 0.5 Step I (kg/mole) 28.7 28.2 28.3 28.8 28.329.8 SD1 (app) 138.0 143.3 138.0 140.0 141.2 140.7 Kg/mole Uncoupled 8.113.2 15.2 6.5 7.7 20.9 Polymer (%) (I) Coupled Linear 31.4 21.1 70.279.3 78.6 16.4 (%) (II) 3-arm (%) (III) 37.8 34.1 5.7 6.3 3.3 46.5 4-arm(%) (IV) 16.1 17.7 2.1 0.9 1.1 12.6 CE (%) 91.3 84.7 83.7 93.0 91.5 78.3PSC (%) 32.5 28.2 29.7 24.4 28.7 32.0 Vinyl (%) 34.4 35.3 35.3 38.7 41.742.6

From these data one can conclude that coupling agents MTMS and IBTMO arethe most promising with respect to coupling efficiency (CE) and lowdegree of branching. Both agents show a high CE over 90% and linearproduct content without significant formation of branched product underthe applied conditions. Although there are some differences in molecularparameters (e.g., PSC and vinyl content) between the various samples itis clear that MTMS and IBTMO outperform the other coupling agents.

More products were prepared with MTMS to check the repeatability andcompatibility with the hydrogenation process. The results for three runswith MTMS are presented in Table 11A.

TABLE 11A Run # 8-7 8-8 8-9 CA MTMS MTMS MTMS 1 2 3 CA/Li 0.5 0.5 0.5StepI (kg/mole) 28.8 26.3 25.4 SD1 (app) 140.0 138.0 126.3 Kg/mole SD1(%)I 6.5 6.8 7.1 Linear (%)II 79.3 83.3 82.7 3-arm (%)III 6.3 3.6 4.14-arm (%)IV 0.9 0.5 0.7 CE (%) 93.0 92.8 93.1 PSC (%) 24.4 n.a 32.8Vinyl (%) 38.7 n.a 40.4

The MTMS coupled product results are very consistent in terms ofcoupling efficiency and linear product formation. Polymer 8-9 washydrogenated at a solids content of 14%. Prior to hydrogenation, andafter coupling, the polymer was first contacted with 2-ethyl hexanol. Afirst batch experiment showed that a complete conversion (residualunsaturation of 0.04 mille-equivalents per gram) was reached after 90minutes at 70° C. with 6 ppm Co. The GPC analysis showed that there wasno decoupling. A sample from hydrogenation in a continuous hydrogenationunit (CHU) was also prepared. The results from both runs are shown belowin Table 11B.

TABLE 11B Hydrogenated Hydrogenated Precursor Batch CHU Linear 82.7 81.482.2 (%)II 3-arm 4.1 4.3 4.2 (%)III 4-arm 0.7 1.5 1.0 (%)IV CE (%) 93.192.5 92.2 PSC (%) 32.8 32.5 32.7

The results of the hydrogenation show that MTMS is a very good candidatefor making hydrogenated polymers since there is no evidence ofdegradation during the hydrogenation.

Example 9

Various tetraethoxy silane coupled, hydrogenated styrene/butadiene blockcopolymers (i.e. (A-B)_(n)X block copolymers) were made in apolymerization process similar to that described in the illustrativeembodiment, 7774, in Example 1 above, and the results are presentedbelow in Table 12. The preparation of these polymers differed from thatdescribed in Example 1 in that 1) these polymers used tetraethoxysilaneas the coupling agent, 2) prior to coupling the molecular weights of theblocks in the living block copolymer were smaller (PS-PBd-Li (A-B-Li));and 3) a Ni/Al hydrogenation catalyst was used. Consistent with theresults in the inventive experiment described in Example 1, the couplingreaction proceeded to give a high level of coupled polymer with goodlinearity in the coupled product. Hydrogenation of these polymersproceeded with a minimum of degradation. The segment molecular weightsfor the coupled linear components of these mixtures are given under theheading “Dimension Linear Polymer”, with the first and third numbersbeing the A block molecular weight in kg/mol, and the second or middlenumber being twice the B block molecular weight in kg/mol. Also givenare the vinyl content of the butadiene units prior to hydrogenation(“(%1,2-butadiene content (%)”), coupling efficiency (“CouplingEfficiency (%), the weight percent of linear 2-arm (“Linear CoupledPolymer (%) (II)” and radial three and four arm species (“BranchedPolymer (%) (III+IV)”), arms %), the weight percent of diblock(“Uncoupled Polymer (%) (I)”), and the weight percent of uncoupleddiblock copolymer following hydrogenation (“Following HydrogenationUncoupled Polymer (%)”). This later measurement is a ready analysis ofthe degree of degradation (decoupling) that occurred duringhydrogenation. The increase in uncoupled polymer on hydrogenation was inthe range of 1–3%; this level of decoupling is not significant from aproduct performance perspective. The sample labeled CP-2 is forcomparison purposes only, and is a hydrogenated styrene/butadiene blockcopolymer that has been prepared by coupling with a different couplingagent. CP-2 has a coupling efficiency of about 68%, a vinyl content ofabout 45%, and molecular weights similar to polymer 9-3. The productlabeled 9-10 is a physical blend of products 9-7, 9-8 and 9-9.

TABLE 12 Summary of Molecular Characteristics of Highly Coupled S-E/B-SPolymers. Linear Dimension Branched Triblock Uncoupled Following Linear1,2- Coupling Polymer Copolymer Polymer Hydrogenation Sample PolymerButadiene Efficiency (%) (%) (%) Uncoupled Number (II) Content (%) (%)(III + IV) (II) (I) Polymer (%) 9-1 5.4-94-5.4 38 96 39 57 4 6 9-25.4-71-5.4 38 96 43 53 4 7 9-3 5.3-72-5.3 48 98 30 68 2 3 9-4 6.2-58-6.238 94 27 67 6 6 9-5 5.7-50-5.7 39 95 24 71 5 6 9-6 5.3-50-5.3 38 94 2866 6 7 9-7 5.5-52-5.5 39 96 21 75 4 9-8 5.5-52-5.5 39 96 21 75 4 9-95.5-53-5.5 38 94 20 74 6 9-10 5.5-50-5.5 38 96 21 75 4 6

Example 10

Highly coupled, very linear, and high vinyl content analogs of thepolymers described in Example 9 were prepared using 1,2-diethoxypropaneas the microstructure modifier instead of diethyl ether. The use of thetetraethoxysilane coupling technology described above gave the polymersdescribed in Table 13.

Hydrogenation using the Co/Al technique described in Example 1 resultedin essentially no decoupling as assayed by GPC (see Table 13).

TABLE 13 Summary of Molecular Characteristics of Highly Coupled, HighVinyl S-E/B-S Polymers Dimension 1,2- Branched Following LinearButadiene Coupling Polymer Linear Uncoupled Hydrogenation Sample PolymerContent Efficiency (%) Polymer (%) Polymer (%) Uncoupled Number (II) (%)(%) (III + IV) (II) (I) Polymer (%) 10-1 7.9-54-7.9 69 91 31 60 9 8 10-26.4-55-6.4 68 93 27 66 7 7The headings used in this table are as defined in Example 9.A polymer of the (CDE)_(n)X type, where n=1, 2, 3, or 4, was preparedusing the coupling technology described in Example 1. Prior to coupling,the polymer was a living triblock copolymer, PBd-PS-PBd-Li. Couplingwith tetraethoxysilane gave the highly linked polymer described in Table13A. This polymer was hydrogenated using Ni/Al to make anE/B-S-E/B-S-E/B, pentablock copolymer. As analyzed by GPC, there was noevidence of decoupling of this polymer during hydrogenation.

TABLE 13A Summary of Molecular Characteristics of Highly CoupledE/B-S-E/B-S-E/B Polymers Linear Following Dimension 1,2-Bd CouplingBranched Polymer Uncoupled Hydrogenation Sample Linear ContentEfficiency Polymer (%) (%) Polymer (%) Uncoupled Number Polymer (%) (%)(III + IV) (II) (I) Polymer (%) 7 5.0-8.2- 77 96 50 46 4 4 57-8.2-5.0

Example 11

Using the polymerization method described for the preparation of 7779 inExample 1, a series of S-Bd-Li polymers were coupled usingtetraethoxysilane, TESi, as the coupling agent. The TESi/P-Li ratio(mol/mol) was varied over a narrow range to assess the optimum ratio ofSi/Li (mol/mol) for good coupling efficiency in combination with highlevels of linearity (minimal levels of branched polymer (“CoupledPolymer 3-arm (III) (%)”) in the product) in the coupled polymerproduct. From the data in Table 14, it is clear that coupling efficiencyis high at Si/Li molar ratios between 0.54 and 0.36. Over this range,the proportion of 2-arm polymer (II) in the coupled product (“CoupledPolymer 2-arm (II) (%)”) increased with increasing molar ratios ofSi/Li. The highest levels of linear coupled polymer were realized atTESi/P-Li (mol/mol)>0.5; at these ratios, over 80% of the coupledpolymer was linear. At TESi/Li (mol/mol)>0.4, over 40% of the coupledpolymer was the linear triblock copolymer, (II). A well coupled linearblock copolymer was prepared over a range of Si/Li molar ratios.

Each of these products was passivated by treatment with 0.1 moles ofMeOH per mole of P-Li moieties which were present prior to the additionof the coupling agent, TESi (The alcohol was actually added to thereactor after the coupling reaction was complete). Hydrogenation of eachof these block copolymer products using the Co/Al technique described inExample 2 for polymer 7919D-H1 gave fully hydrogenated rubber segments(over 98% of the C═C centers were saturated), S-E/B-S polymers, with nosignificant loss in coupled polymer content.

TABLE 14 Affect of TESi/P-Li Ratio on Coupling Efficiency and Linearityfor Coupled S-Bd-Li. Coupled Coupled Coupling Product Product ExperimentTESi/P-Li Efficiency 2-arm (II) 3-Arm (III) Number (mol/mol) (%) (%) (%)1 0.58 89.2 85.8 13.6 2 0.54 92.8 81.7 16.7 3 0.54 94.6 79.8 17.9 4 0.5490.7 81.6 16.5 5 0.52 94.4 80.8 18.4 6 0.52 93.5 80.9 17.5 7 0.50 95.675.0 24.0 8 0.50 95.6 73.7 25.2 9 0.49 96.3 74.4 24.3 10 0.48 97.1 71.028.1 11 0.47 96.4 68.1 30.6 12 0.46 97.0 63.6 36.4 13 0.45 97.2 66.333.7 14 0.44 96.5 61.0 37.8 15 0.44 96.6 59.5 39.3 16 0.44 97.0 60.038.8 17 0.43 96.4 65.4 32.9 18 0.43 96.8 53.3 46.7 19 0.43 96.7 52.546.6 20 0.42 96.3 42.6 56.1 21 0.42 96.4 46.3 52.6 22 0.41 96.7 54.244.1 23 0.41 96.1 45.7 54.3 24 0.4 97.0 50.9 48.3 25 0.4 96.5 41.1 57.626 0.39 96.6 32.4 66.3 27 0.39 96.6 31.1 67.6 28 0.39 97.3 38.4 61.6 290.39 97.4 33.8 66.2 30 0.36 93.2 5.0 90.8 31 0.33 87.6 8.9 87.0

Example 12

In this example two comparative polymers with isoprene/butadienemidblocks were prepared, along with one polymer according to the presentinvention. Comparative polymer A (CP-A) was prepared by sequentialpolymerization of the first styrene block, followed by the mixed dieneblock, and then the second styrene block, as described below: 60 kg ofcyclohexane and 15 kg, of styrene were charged to a reactor. The reactortemperature was increased to about 40° C. Impurities were removed byadding small aliquots of s-butyllithium until the first evidence ofcolor. 992 mL of a solution of an approximately 12% wt solution ofs-butyllithium in cyclohexane was added, and the styrene was allowed tocomplete polymerization at about 60° C. The molecular weight of thepolystyrene produced in this reaction was determined to be 11,050 AMU byGPC. 290 kg of cyclohexane, 14.8 kg of butadiene and 14.9 kg of isoprenewere added to a second reactor. The temperature was adjusted to about60° C. and impurities were removed by adding small aliquots ofs-butyllithium until the first evidence of color. 63.6 kg of thepolystyryllithium solution produced in the first reactor was thentransferred into the second reactor. The temperature was maintained at60° C. After about 10 minutes, 14.9 kg of butadiene and 14.9 kg ofisoprene were added, both at a rate of about 500 g/min. The reaction wasallowed to proceed at 60° C. until the polymerization of both monomerswas essentially complete. A sample collected at this point was analyzedby ¹H NMR and GPC. The sample had a styrene content of 18.6% wt, 52% wtof the diene monomer was comprised of isoprene and the overall molecularweight was 55,800. 12 kg of styrene was added, and the the reaction wasallowed to proceed until all of the styrene was consumed. Water (88 mL)and carbon dioxide were added to terminate the reaction. The finalproduct had a styrene content of 31%, and an overall molecular weight ofabout 69,000.

Comparative polymer B (CP-B) was prepared essentially as describedabove, except a small amount of isoprene was charged at the end of thediene polymerization, in order to insure that all of the living chainsterminated in isoprene repeat units. 60 kg of cyclohexane and 15.1 kg,of styrene were charged to a reactor. The reactor temperature wasincreased to about 40° C. Impurities were removed by adding smallaliquots of s-butyllithium until the first evidence of color. 1000 mL ofa solution of an approximately 12% wt solution of s-butyllithium incyclohexane was added, and the styrene was allowed to completepolymerization at about 60° C. The molecular weight of the polystyreneproduced in this reaction was determined to be 11,400 AMU by GPC. 291 kgof cyclohexane, 15 kg of butadiene and 15 kg of isoprene were added to asecond reactor. The temperature was adjusted to about 60° C. andimpurities were removed by adding small aliquots of s-butyllithium untilthe first evidence of color. 63 kg of the polystyryllithium solutionproduced in the first reactor was then transferred into the secondreactor. The temperature was maintained at 60° C. After about 10minutes, 15 kg of butadiene and 13.4 kg of isoprene were added at such arate as to ensure that both monomers were added over the course of about30 minutes. The reaction was allowed to proceed at 60° C. until thepolymerization of both monomers was essentially complete, and then anadditional 1.5 kg aliquot of isoprene was added. A sample collected atthe end of the diene polymerization was analyzed by ¹H NMR and GPC. Thesample had a styrene content of 18.1% wt, 51% wt of the diene monomerwas comprised of isoprene and the overall molecular weight was about63,500. 12.4 kg of styrene was added, and the the reaction was allowedto proceed until all of the styrene was consumed. Water (88 mL) andcarbon dioxide were added to terminate the reaction. The final producthad a styrene content of 30.9%, and an overall molecular weight of about75,900.

Polymer 1-1 was prepared by tetra-ethoxy silane coupling, as describedbelow: First, the diblock polymer anion in which the diene block iscomprised of a copolymer of budadiene and isoprene (50:50 wt:wt),S-Bd/Ip-Li, is prepared as follows 96 kg of cyclohexane and 24.1 kg, ofstyrene were charged to a reactor. The reactor temperature was increasedto about 40° C. Impurities were removed by adding small aliquots ofs-butyllithium until the first evidence of color. 1,570 mL of a solutionof an approximately 12% wt solution of s-butyllithium in cyclohexane wasadded, and the styrene was allowed to complete polymerization at about60° C. The molecular weight of the polystyrene produced in this reactionwas determined to be 11,270 AMU by GPC. 170 kg of cyclohexane, 10.5 kgof butadiene and 10.5 kg of isoprene were added to a second reactor. Thetemperature was adjusted to about 60° C. and impurities were removed byadding small aliquots of s-butyllithium until the first evidence ofcolor. 90.5 kg of the polystyryllithium solution produced in the firstreactor was then transferred into the second reactor. The temperaturewas maintained at 60° C. After about 10 minutes, 10.5 kg of butadieneand 10.5 kg of isoprene were added, both at a rate of about 500 g/min.The reaction was allowed to proceed at 60° C. until the polymerizationof both monomers was essentially complete. A sample collected at thispoint was analyzed by ¹H NMR and GPC. The sample had a styrene contentof 31% wt, 51% wt of the diene monomer was comprised of isoprene and theoverall molecular weight was 36,400. 163.5 g of TEOS was added, and thecoupling reaction was allowed to proceed for 60 minutes at 60° C. Water(88 mL) and carbon dioxide were added to terminate the reaction. Thefinal product had a coupling efficiency of 93%, and 93% of the coupledspecies were linear, the remaining being 3-arm radial.

1. A process for making a hydrogenated block copolymer, comprising the steps of: a. reacting a living lithium-terminated polymer having the formula P-Li where P is a copolymer chain of one or more conjugated dienes having from 4 to 12 carbon atoms and one or more mono alkenyl arenes having from 8 to 18 carbon atoms with an alkoxy silane coupling agent having the formula R_(x)—Si—(OR′)_(y), where x is 0 or 1, x+y=4, R and R′ are the same or different, R is selected from aryl hydrocarbon radicals, linear alkyl hydrocarbon radicals and branched alkyl hydrocarbon radicals, and R′ is selected from linear and branched alkyl hydrocarbon radicals, and where the molar ratio of Si to Li is from about 0.35 to about 0.7, thereby forming a coupled polymer; b. hydrogenating the coupled polymer under hydrogenation conditions to substantially saturate at least the olefinically derived double bonds of said coupled polymer without substantial degradation of the coupled polymer; and c. recovering the resulting hydrogenated polymer; wherein the resulting hydrogenated block copolymer comprises a mixture of from 0 to 5 weight percent tetra-branched block copolymer, from 0 to 60 weight percent tri-branched block copolymer, from 40 to 95 weight percent di-branched block copolymer and from 2 to 10 weight percent linear diblock copolymer.
 2. The process according to claim 1 wherein said conjugated diene is selected from the group consisting of butadiene and isoprene and said mono alkenyl arene is styrene.
 3. The process according to claim 2 wherein P is a block copolymer of styrene and butadiene with the butadiene block being adjacent to the lithium ion.
 4. The process according to claim 3 wherein the styrene block has an average molecular weight of from about 3,000 to about 60,000 and said butadiene block has an average molecular weight of from about 20,000 to about 200,000.
 5. The process according to claim 3 wherein said alkoxy silane coupling agent is a tetra alkoxy silane where x is zero and R′ is a linear or branched alkyl hydrocarbon radical having 1 to 12 carbon atoms.
 6. The process according to claim 5 wherein said alkoxy silane coupling agent is tetramethoxy silane and wherein the coupled polymer is contacted with an alcohol prior to hydrogenation.
 7. The process according to claim 6 wherein said alcohol is methanol and the molar ratio of methanol to Li is from 1 to 1.5 moles of methanol per mole of Li.
 8. The process according to claim 5 wherein said alkoxy silane coupling agent is tetraethoxy silane.
 9. The process according to claim 8 wherein the coupled polymer is contacted with an alcohol prior to hydrogenation.
 10. The process according to claim 9 wherein said alcohol is methanol and the molar ratio of methanol to Li is from 0.05 to 0.5 moles of methanol per mole of Li.
 11. The process according to claim 5 wherein said hydrogenation takes place at a temperature of between about 20° C. to about 60° C.
 12. The process according to claim 11 wherein the catalyst used in the hydrogenation is selected from cobalt, nickel and titanium catalysts.
 13. The process according to claim 12 wherein the coupled polymer is contacted with an alcohol prior to hydrogenation.
 14. The process according to claim 3 wherein said alkoxy silane oupling agent is an alkyl trialkoxy silane.
 15. The process according to claim 14 wherein said alkyl trialkoxy silane is methyl trimethoxy silane.
 16. The process according to claim 15 wherein the coupled polymer is contacted with an alcohol prior to hydrogenation.
 17. The process according to claim 16 wherein said alcohol is 2-ethyl hexanol and the molar ratio of alcohol to Li is from 0.05 to 0.5 moles of alcohol per mole of Li.
 18. The process according to claim 3 wherein said alkoxy silane is an aryl trialkoxy silane.
 19. The process according to claim 18 wherein said aryl trialkoxy silane is phenyl trimethoxy silane and the coupled polymer is contacted with an alcohol prior to hydrogenation.
 20. The process according to claim 19 wherein said alcohol is 2-ethyl hexanol and the molar ratio of alcohol to Li is from 0.05 to 0.5 moles of alcohol per mole of Li.
 21. The process according to claim 1 wherein the coupling efficiency is greater than 90%.
 22. The process according to claim 1 wherein the molar ratio of Si to Li is from about 0.4 to about 0.55.
 23. The polymer produced by the process of claim
 7. 24. The polymer produced by the process of claim
 10. 25. The polymer produced by the process of claim
 17. 26. The process according to claim 2 wherein P is a block copolymer of styrene and isoprene with the isoprene black being adjacent to the lithium ion.
 27. The process according to claim 26 wherein the styrene block has an average molecular weight of from about 3,000 to about 60,000 and said isoprene block has an average molecular weight of from about 20,000 to about 200,000.
 28. The process according to claim 26 wherein the alkoxy silane coupling agent is selected from tetramethoxy silane, tetraethoxy silane, tetrabutoxy silane, tetrakis(2-etylhexyloxy)silane, methyl trimnethoxy silane, methyl triethoxy silane, isobutyl trimethoxy silane and phenyl trimethoxy silane.
 29. The process according to claim 4 wherein the alkoxy silane coupling agent is selected from tetramethoxy silane, tetraethoxy silane, tetrabutoxy silane, tetrakis(2-ethylhexyloxy)silane, methyl trimethoxy silane, methyl triethoxy silane, isobutyl trimethoxy silane and phenyl trimethoxy silane. 